Victories over Italy and Ireland had allowed Scotland to dream of a first title since 1999, but defeat to the defending champions last year ended that hope.
Scott Johnson's side will complete their campaign against France in Paris knowing victory will see them finish ahead of the 2011 World Cup finalists.
And after finding their feet under interim boss Johnson, Harley admits Scotland must shut out the defeat to Wales and show what they are capable of against France.
"We have come a long way. Some of the things we have been doing, we haven't done before," he said.
"The tightness of the squad helps and some of the rugby we have played and tries we have scored, the pressure we have put on teams has shown great progress.
"It is up to us to acknowledge what we have done wrong and build on the positives so we can keep getting better as a squad.
"We would potentially have been in the mix for the championship had we beat Wales but that is out the window.
"But our championship now comes down to the last week and it is a chance for us to show the potential of the side and to put together a complete performance and show a defensive display that we know we are capable of."